1. Field of the Invention
This invention relates to video display devices, and more particularly, to a display system.
2. Description of Prior Art
A reference of record is the Burnham et al, U.S. Pat. No. 3,784,742. Cathode ray tubes have face plates which are spherically shaped, and as such, are prone to reflect all ambient room illumination that exists in the frontal hemisphere. This by itself dilutes the brightness of the display and reduces the contrast, thus making the display less readable and causing considerable eyestrain. Additionally, reflections off the face of the CRT of all bright objects in the vicinity, cause added visual confusion contributing to eyestrain and fatigue. Recently, special face plates have been devised as covers for the CRT's. Such covers or dark covers made of anti-reflection polaroid or of polaroid-quarter waveplate sandwiches do reduce glare, but they also dim the display so that little gain, if any, is made in readability. Special glare reducing spectacles are also available for each color video display terminal or (VDT's) associated with all types of computers, but these devices must be prescription ground for each individual observer, and they do not overcome the problems of fatigue and eyestrain due to close viewing, nor do they avoid cumulative effects of electron radiation from the CRT. Other disadvantages of current VDT's are the concentration required by the operator at a close viewing distance (approximately fourteen inches) leading to fatigue in viewing, blurred vision, eye irritation, tearing, headaches, etc., and most recently discovered, electron radiation effects from the CRT, which may be cumulative and harmful after long exposures. The display system in accordance with the present invention, will avoid all of the aforementioned disadvantages of available VDT's through the use of an indirect viewing optical system.
The principal object of this invention is to provide a display system, which will be unique for employment in viewing either television presentations or film projection, by reducing eyestrain and glare from light reflections, and by increasing contrast and apparent brightness, making the presentation more readable.
Another object of this invention is to provide a display system, which will be employed to substantially reduce all harmful radiation effects from the electrode or cathode ray tube, to insignificant levels, as video display terminal operators are presently subjected to electron radiation which may be cumulative and harmful after long exposures thereto.
A further object of this invention is to provide a display system, which will be an improved means to project a CRT to a comfortable viewing distance, such as, two to three feet distant from the observer, but not to infinity. The present invention will be of such design, as to have the focal length of the optical systems selected to magnify the CRT image, so that the apparent size of the CRT is larger at a three foot distance than the actual CRT appears to be at fourteen inches.